1. Field of the Invention
This invention relates to a travelling working machine with winches.
2. Description of the Related Art
FIG. 8 shows a telescopic boom type crane. An upper rotating body 52 is mounted rotatably on a lower travelling body 51 with crawlers 50. A telescopic boom is mounted on the upper rotating body 52 so as to be capable of rising and lowering. The reference numeral 54 is a cylinder for rising and lowering the boom 53.
A main winding rope 55a taken from a main winch 55 hangs up a main lifting hook 55b and an auxiliary rope 56a taken from an auxiliary winch 56 hangs up an auxiliary hook 56b, respectively.
As overhang of the boom in transport condition is too large, it is required to dispose the boom 53 and a boom supporting frame 52a as rearward as possible. In order to improve a workability or working efficiency at a limited space, it is required to make a rotating rear radius R (a distance from a rotating center to a rear end of the upper rotating body) of a crane like this as small as possible. Furthermore, a regulated transport condition limits a transverse width of the upper rotating body. As a result, there is not enough space on it to dispose the winches.
For saving the space, Japanese Patent Application Publication No. Hei 2001-316080 discloses a structure that, at a rearward portion (rear frame) of a boom supporting frame, winches are mounted in such a manner that two of them are disposed at left and right sides respectively of a lower portion of the frame and the other one is disposed at an upper portion thereof.
When the winches are disposed densely like this and a counterweight is mounted on a bracket at a rear frame with a sufficient strength has to be prepared so as to support load of the winches and the counterweight and so on.
In the meantime, when a winch with a transverse width which is longer than a width of a rear frame is used, it is necessary to form openings of the rear frame which have enough space for a flange, for example, as a maximum diameter-portion of the winch to pass through. Accordingly, the greater capacity of winding up the winch mounted on the rear frame has, the larger diameter the flange has. As a result, as the openings have to be larger in diameter according to the larger diameter, it is difficult to obtain a required strength of the rear frame.